Current understanding of the cellular neurophysiology of arthropod visual systems is limited to a few examples. A great deal is known about the function of individual photoreceptors from intracellular recordings. They respond with a graded depolarizing receptor potential, have a limited angle of acceptance, and cannot distinguish between different parameters of photic stimuli such as intensity, wavelength, polarization angle, or movement. Extracellular measurements of activity of higher order interneurons and results of behavioral experiments indicate that these stimulus features are extracted by the nervous system from many simple inputs and/or manifest themselves as being important for behavior. The objective of the proposed research is to understand the cellular basis for such integrative capabilities. To accomplish this, studies will concentrate on visual systems which offer certain features that are open to experimentation. These are: a) the cockroach Periplaneta whose retina contains two spectrally and temporally distinct photoreceptor classes and whose cellular biology permits selective ablation experiments to isolate portions of the visual system; b) the marine decapod crustaceans Carcinus and Callinectes whose visual systems would appear to permit experimental isolation of the mechanisms of detection and transmission of information regarding the orientation of the plane of polarized light. Experiments seek to record and classify unit activity at several peripheral levels of these visual systems, morphologically identify the responding elements, and to manipulate the systems through surgical modification and/or selective adaptation in the hope of being able to infer the nature of cellular interactions occurring there.